1. Field of the Invention
The present invention relates to a shifting apparatus for a vehicle transmission arranged at an instrument panel portion of the vehicle or at a near region thereof, and more particularly to a shifting apparatus for a vehicle transmission which is able to absorb the shock when the shock load is applied to a shift operation section of the shifting apparatus.
2. Description of Background Art
In general, although the shifting apparatus including a shift lever for a manual transmission or a selector lever for an automatic transmission is arranged at a center console between a driver""s seat and an assistant driver""s seat, there has been recently developed a shifting apparatus designed to be arranged at an instrument panel of the vehicle or at a near region thereof.
That is, the arrangement of the shifting apparatus for a vehicle transmission at a instrument panel portion of the vehicle or at a near region thereof makes it possible to ensure a sufficient space for front seats and thus to prevent the passengers from erroneously touching the shift lever or selector lever, and also to ensure an arrangement of the shift lever or selector lever near a steering wheel and thus enabling quick motion of the driver""s hand from the steering wheel to the shift lever or selector lever, and vice versa.
One example of technology of shock absorbing means for absorbing the shock applied to the operation lever such as the shift lever or selector lever is disclosed, for example, in Japanese laid-open patent publication No. 16597/1998 (hereinafter referred to Prior Art 1).
Such a shock absorbing means comprises a supporting member for pivotably supporting a shift operation section around a point on the body of a vehicle and a rod-shaped member interposed between the shifting apparatus and the supporting member of the vehicle. One end of the rod-shaped member is connected to the shifting apparatus and the other end thereof is connected to the supporting member of the vehicle so that the rod-shaped member restrains the pivotal movement of the shift operation section and absorbs the shock load with permitting the pivotal movement of the shift operation section due to breakage of the rod-shaped member or release thereof from the supporting member or the shifting apparatus when a shock load exceeding a predetermined value is applied to the shifting apparatus.
Another shock absorbing means for effectively absorbing both the initial shock load and the shock load following the initial shock load is disclosed in Japanese laid-open patent publication No. 30669/1998 (hereinafter referred to Prior Art 2).
Such a shock absorbing means is used for a shaft of a shift lever and comprises a cylindrical tube 101 having predetermined dimensions and an energy absorbing member 102, a portion thereof being inserted in the cylindrical tube 101 as shown in FIG. 17.
The energy absorbing member 102 has a distal end 102a having a diameter substantially corresponding to the inner diameter of the cylindrical tube 101, an enlarged diameter portion 102b having a diameter larger than that of the distal end 102a, a diverging portion 102c diverging from the distal end 102a to the enlarged diameter portion 102b at an angle xcex81, and a shoulder portion 102d connecting the diverging portion 102c and the enlarged diameter portion 102b at an angle xcex82 which is larger than the angle xcex81.
When a force F is applied to the energy absorbing member 102 by a certain shock, the energy absorbing member 102 is forced into the cylindrical tube 101 and thus the shock load is absorbed by the deformation of the opening of the cylindrical tube 101, the diverging portion 102c and the enlarged diameter portion 102b. 
The initial shock load P1 and the following shock load P2 are determined by setting the angle xcex81 of the diverging portion 102c and the angle xcex82 of the shoulder portion at the manufacturing stage of the energy absorbing member 102. That is, the initial shock load P1 can be set at a relatively low level by reducing the angle xcex81, and the following shock load P2 can be set at a relatively high level by increasing the angle xcex82. Accordingly, it is possible to obtain an ideal load-displacement curve shown in FIG.18 by appropriately setting the angles xcex81 and xcex82.
However, both the Prior Arts 1 and 2 include following problems. That is, in the Prior Art 1, since the shift operation section becomes a free condition separated from the body of the vehicle after the rod-shaped member having been broken or released from its connection by the shock load, it is impossible to absorb the shock load after the breakage or disconnection of the rod-shaped member.
In the Prior Art 2, although it is possible to set the initial shock load and the following load, it is difficult to properly set the initial shock load and to ensure the static strength of the structural members i.e. the energy absorbing member, since the absorption of the shock load is carried out based only on the deformation of the structural members not on the breakage thereof. In addition, since both the initial shock load and the following shock load are adjusted by only one mounting portion, it is difficult to properly set the design shock load.
It is, therefore, an object of the present invention to provide a shifting apparatus for a vehicle transmission being able to easily adjust the initial shock load and the following shock load over a predetermined stroke in which shock loads each having different characteristic curve such as shown in FIGS. 13(a) and (b) are absorbed by separate mounting portions and the initial shock load is absorbed by the breakage of the shock absorbing members not by the deformation thereof in order to ensure the static strength of the shock absorbing members.
For achieving the object mentioned, there is provided, according to the present invention, a shifting apparatus for a vehicle transmission comprising a shift operating section for supporting an operation level and mounting members for arranging the shift operation section at an instrument panel portion of the vehicle or at a near region thereof characterized in that said mounting members are adapted to mount the shift operation section on a body of the vehicle at least two places thereof, and each of the mounting members is provided with a first shock absorbing member adapted to be broken to absorb an initial shock load as well as a second shock absorbing member adapted to be deformed or broken over a predetermined stroke to absorb a shock load following the initial shock load when a shock load exceeding a predetermined value is applied to the shift operation section.
According to this structure, the first shock absorbing member is broken and the second shock absorbing member is broken or deformed over a predetermined stroke when the shock load is applied to the shift operation section. That is, the initial shock load P1 and the following shock load P2 each having a characteristic curve respectively shown in FIGS. 13(a) and (b) are separately absorbed by separate shock absorbing members.
Additionally, there is provided a shifting apparatus for a vehicle transmission wherein said first shock absorbing member is a rib formed integrally with the shift operation section and adapted to be broken by each of the mounting member displaced relatively to the shift operation section when said shock load is applied to the shift operation section.
According to this structure, the initial shock load is absorbed by the breakage of the ribs formed integrally with the shift operation section.
Further, there is provided a shifting apparatus for a vehicle transmission wherein said second shock absorbing member comprises a plate-shaped portion extending from the mounting member and a restraining portion formed integrally with the shift operation section for restraining the plate-shaped portion.
According to this structure, the shock load is absorbed by the breakage of the restraining portion acted by the plate-shaped portion, or by the deformation of the plate-shaped portion acted by the restraining portion when the mounting members and the shift operation section are relatively moved by the application of the shock load. Since the breakage of the restraining portion is continuously carried out by the region in which the restraining portions exist, the shock load is absorbed over a predetermined stroke.
Furthermore, there is provided a shifting apparatus for a vehicle transmission wherein said plate-shaped portion is formed with a slit for aiding the deformation of the plate-shaped portion when the shock load is applied to the shift operation section.
According to this structure, each plate-shaped portion deforms along its slit and absorbs the shock load when the shock load is applied.
In addition, there is provided a shifting apparatus for a vehicle transmission wherein a said plate-shaped portion is formed with projections for deforming or breaking the restraining portion during relative movement between the plate-shaped portion and the shift operation section when the shock load is applied to the shift operation section.
According to this structure, the restraining portion is broken by the projections when the plate-shaped portion and the shift operation section are relatively moved by the application of the shock load.
Also, there is provided a shifting apparatus for a vehicle transmission wherein the surfaces of the projections of the plate-shaped portion is offset from the direction of the relative movement between the plate-shaped portion and the shift operation section.
According to this structure, a degree of the breakage of the projections is adjusted by the offset angle.
Further, there is provided a shifting apparatus for a vehicle transmission wherein said first shock absorbing member and said second shock absorbing member comprise insert potions connecting the shift operation section and the mounting member.
Furthermore, there is provide a shifting apparatus for a vehicle transmission wherein said first shock absorbing member comprises pin-shaped insert portions.
Additionally, there is provided a shifting apparatus for a vehicle transmission wherein said second shock absorbing member comprises plate-shaped insert portions.